Pathophysiology

• The bundle branches of the cardiac conduction system arise from the bundle of His as it exits the atrioventricular node.
• In human beings, the left bundle branch can often be divided into an anterior and a posterior fascicle. Selective block of the anterior fascicle results in deviation of the ECG mean electrical axis to the left.
• The anatomy of the canine left bundle branch is not easily categorized in this way and the terminology left anterior fascicular block is likely a misnomer in this species. Experimental damage to the left anterior portion of the canine bundle branch does not cause the typical ECG pattern ECG: overview seen in humans with this condition, and the author and many others prefer to describe such axis shift when it does occcur in dogs simply as a "left axis shift (or deviation)", rather than use it as evidence of a "left anterior fascicular block".

ECG characteristics

Clinical importance

Treatment

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.